In addition to mountains produced by corrugation and upheaval, there are also in the middle American region numerous volcanic mountains. Of these there are two well-defined belts, each trending in general north and south, or directly across the longer axes of the folds of the Antillean mountains. One of these belts of volcanic cones and craters is situated on the Pacific coast of Central America and Mexico, and includes some 25 active volcanoes, and the other is defined by the numerous volcanic islands of the Lesser Antilles. The association of these belts of fracture through which molten rock has been extruded and where earthquakes are of common occurrence, with the junction of the east and west belt of plication to which the Antillean mountains are due, with the north and south belts of mountains forming the Pacific and Andean cordilleras, is significant in connection with the study of the origin of the larger features of the relief of the solid earth. * * * * * Varied as is the relief of North America when studied in detail, an outline sketch of its major features may be readily retained in mind. On the east side of the main continental area are the Atlantic mountains, extending from near the Gulf coast northward to beyond Hudson Strait; in the central part is the broad continental basin, a vast region of low relief reaching from the Gulf of Mexico to the Arctic Ocean; west of the continental basin are the Pacific mountains, the greatest of all the elevations on the continent, which begin abruptly in south-central Mexico and extend northward, expanding to a width of about 1,000 miles in the United States and reach the Arctic Ocean and Bering Sea. The movements in the earth's crust, which blocked out these major physiographic features, were produced by forces acting in east and west directions, and gave origin to folds and faults with their longer axes trending north and south. To the south of the main body of the continent, in middle America, are situated the Antillean mountains, also a cordillera comparable with the Atlantic and Pacific cordilleras, in which the longer axes of the folds and faults trend east and west, and are due to forces acting in north and south directions. The Antillean mountains in a general way connect or intervene between the Pacific and the Andean cordilleras. Where the Antillean mountains cross the axes of the Pacific and Andean cordilleras are situated the volcanoes of southern Mexico and Central America, and those of the Lesser Antilles. Geographers will recognise that this outline is drawn boldly, but although it will no doubt have to be modified as detailed studies progress, it should serve to emphasize the leading geographic divisions of the North American continent when viewed as a whole. LITERATURE